Fix crash when updating in libsvn_wc/update_editor.c, window_handler().

* subversion/libsvn_wc/update_editor.c
  (window_handler): Remove temporary file only if it already created by
   lazy_open_target().


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1513156 13f79535-47bb-0310-9956-ffa450edef68